Aluminum: a Potential Solution to the Grid Storage Problem. Vision for World-Wide Electrical Power Dr. Arthur Davidson Davidson AJH LLC Pittsburgh, PA 1 With thanks to Prof. Jerry Woodall, Purdue University, National Medal of Technology Laureate

Coal burning cycle: 10 7 years 2 Secondary Aluminum Coal Deposit CO 2 + ash Energy In Energy Out Carbon Life Forms

Aluminum energy cycle: 10 days 3 Secondary Aluminum Aluminum Alloy Hydrated Alumina + In, Ga, Sn Energy In Energy Out Secondary Aluminum

Electrical energy will reduce alumina, and water will oxidize aluminum: 4 2Al +3H 2 O = Al 2 O 3 + 3H kWh/kg 2Al 2 O 3 + 3C + 15kWh/kg = 4Al +3CO 2 Thus, aluminum can store and retrieve energy, IF the second reaction proceeds. Bio recycle Industrial recycle

How does it work? Aluminum loves oxygen As a result, a skin of alumina (Al ) forms on air-exposed pure Al and protects it from further rapid oxidation If this passivating oxide is disrupted, Al would react with water to produce hydrogen This can be done slightly above room temperature by dissolving Al into liquid gallium (Ga) When this liquid alloy contacts water, hydrogen is generated via Al in the Ga diffusing to the water-liquid metal interface where it splits water into hydrogen, alumina; the alumina is no longer protective 5

Energy Density: Al  H 2 +heat As hydrogen from splitting water: As hydrogen from splitting water: 1 Kg H 2 : 142 MJ = 39.4 kWh combustible energy 1 Kg H 2 : 142 MJ = 39.4 kWh combustible energy 1 Kg Al makes 111 g of H 2 from 2 Kg of H 2 O = 4.3 kWh 1 Kg Al makes 111 g of H 2 from 2 Kg of H 2 O = 4.3 kWh As heat from splitting water: As heat from splitting water: 1 Kg Al: 4.3 kWh 1 Kg Al: 4.3 kWh Total energy, 1 Kg Al: 8.6 kWh (1Kg coal: 6.7 kWh!) Total energy, 1 Kg Al: 8.6 kWh (1Kg coal: 6.7 kWh!) Energy to electrolyze alumina to 1 Kg of Al: 12.9 kWh Total energy efficiency: (8.6/12.9) x 100 = 66% Energy to electrolyze alumina to 1 Kg of Al: 12.9 kWh Total energy efficiency: (8.6/12.9) x 100 = 66% 6 Woodall

Self Contained (battery-like) kWh/kg Nitroglycerin1.772 Lithium ion nanowire Batt0.706 Sodium Sulfur Battery0.200 Lead Acid Battery0.039 Hydro electric Fuels: Need oxygen source kWh/kgkWh/liter Hydrogen (liquid) Boron Gasoline Aluminum Bituminous coal Wood Some energy storage densities 7

Where does aluminum come from? Crush, grind, caustic soda, make slurry Digest, settle, precipitate crystals Calcining kiln makes dry crystals of Al 2 O 3 Na 3 AlF 6 (cryolite) electrolyte Carbon anode captures oxygen, makes CO to 15 kWh per kg of Aluminum $1.76 /kg 1 kg $0.66 /kg $2.42 /kg 4 kg

95 wt.% Al – 5 wt.% GaInSn (vendor alloy) 95 wt.% Al – 5 wt.% GaInSn (vendor alloy) 9 Woodall

Al in Ga Splitting Water to make Hydrogen! 10 Woodall

Important facts about making aluminum Bauxite ore mined and dressed to extract alumina Alumina is chemically purified to 4-9s purity Purified alumina is sized to a powder with a mean particle size of 120 micrometers If done by Alcoa in Australia it is shipped to one of their nine smelters around the world Batches of Al with customer specified impurities are made by electrolysis of high purity alumina Spent Al products are mostly sent to scrap yards Most of this scrap Al metal with impurities is currently not recycled because it’s cheaper to purify alumina than impure Al! 11 Woodall

Backscattered electron photomicrograph of 95-5 sample showing In and Sn in the grain boundaries Woodall

So, how does the solid Al rich alloy split water? The data supports the following model: The liquid Ga,In,Sn phase between the grains continuously dissolves Al and this Al in solution splits water Woodall

Legend: Al-Ga grain AlloyWater At room temperature, the Ga-In-Sn phase(s) liquefy. Al is able to move freely through the liquid phase. Al near the surface contacts the water interface. The ensuing exothermic reaction produces hydrogen as the Al is oxidized. Woodall’s explanation of the reaction between Al and H 2 O Al Ga, In, Sn HO H

Reaction rate Studies: 50 wt% Al - 50 wt% (Ga,In,Sn) moles of H 2 per 0.5 g Al theoretical yield – Woodall

Where are we now? We can now make solid and bulk Al rich alloys (95 wt% Al, 5 wt% Ga,In,Sn) that split water at temperatures between ice (0C) and steam (>100C) and make H 2 on demand Woodall

Will adding an aluminum plant to a wind farm make electricity cheaper? 17 Cost = W + Al(variable) + Al (capital) Energy out increased by f W = 70%?? Cost/Energy = {[W + Al(variable) + Al (capital)] / (1+f W )} W is the cost of the windfarm, $0.10 per kWhr ?? Energy cost for aluminum plant: $0.00 per kWh Capital cost of Qatar plant amortized over 50 year output: $0.023 per kWh Variable aluminum costs (anodes, scrubbing, transport, …) $0.10 per kWh ??

EV car battery cost basis 18 Nissan Leaf, 24 kWh cost: $18,000 8 years of daily recharging, 2880 cycles Cost of $0.10/kWh : 24kWh x $0.10 x 2880 = $7000 Cost of energy for 2880 cycles: $25,000. Total energy purchased: 24kWh x 2880 cycles = 69,120 kWh. Cost/kWh = 25,000 / 69,120 = $0.36 / kWh

Market Aluminum cost basis 19 Market price of structural aluminum: $2.42 / kg If ¾ of this price is the Bayer process, the price could come down to ~$1.00 /kg If turbines are 35% efficient, and energy density of Al is 8.6 kWh/kg Then $1.00 of Al produces 3.01 kWh of electricity, or $0.33 / kWh Cost/kWh = $0.33 / kWh

Rough economic comparison 20 Leaf type battery extended to grid: $0.36 / kWh over lifetime of plant Aluminum alloy grid storage: $0.33 / kWh continuously

Vision of Davidson AJH LLC Turbine power generation plants, green aluminum reduction plants, and non-fossil energy sources will all be coupled geographically and economically. Regions around the world will look like Ravenswood, WV Trains and barges will ship aluminum alloy like they ship coal now 21

. 500 MW Burns this in 2 days ,000 coal miners at work in the US to keep the internet working.

Ravenswood Aluminum Plant 23

Ravenswood Coal Plant 24

Turbine + Aluminum Plant + Windfarm 25

Cheswick power plant coal stockpile 26

Machine to empty coal barge 27

Reactor and turbine building 28

Catwalk by coal conveyer 29

Comparative costs of energy storage materials and devices to supply 1 kWh of energy Coal: $0.004 Natural Gas: $0.03 Al: $0.05 (hydrogen plus heat) using scrap metallic Al Gasoline: $0.09 (at $3.00/gallon) Li ion battery: $

What about Ga, In, and Sn? Ga,In and Sn are inert and totally recoverable. Experiments have recycled the Ga used in water splitting solid alloys up to 32 times. Currently, the 60 ton market for Ga is for electronics with purities between 4 and 7-9s, about $0.60/gm! This process uses low purity Ga, In, Sn and low purity Al and tap water/non potable water. With recycling, a price of the alloy component could be $0.70 /kg. Woodall estimated that alloys with <5% Ga there is enough economically recoverable Ga to run 10 9 cars. Woodall

The End Dr. Arthur Davidson Davidson AJH, LLC Pittsburgh, PA

Experimental reactor and pressure controller Up to 20 Kg of alloy (88 kWhrs of H 2 ) Woodall

Electricity costs to reduce Al +3 to Al The electrochemistry of reducing Al (in alumina) is: Al e - -- > Al, and requires about 12.9 kW-hr/kg of Al at a present efficiency of 67% [(8.8/12.9) x100 = 68%] Using autos with ICEs, the Prius for example: 2.9 Kg. Al will produce the same amount of energy in the form of hydrogen as 1 Kg of gasoline, i.e., 12.8 kW- hr At 50 mi/gal, it takes 6 gallons x 2.7 Kg/gal. = 16.2 Kg of gasoline to drive a Prius car 300 mi, or 47 Kg of Al* At $3.00/gal for gasoline and $2.40/Kg** for Al, the trip costs $18 using gasoline and $112 using Al (ouch!) *60 Kg. on-board water will be required, assumed to be a negligible cost and a 80% recovery rate for continuous reuse. **Current spot market price

For an Al recycler next to a nuclear power plant* with an on-site power production cost of $0.02/kW-hr, the Al can be recycled from alumina back to Al for: 12.9 kWh/Kg x $0.02/kWh = $0.26/Kg of Al** $0.75; ($0.75/12.8) = $0.06/kWh 2.9 Kg Al production cost: $0.75; ($0.75/12.8) = $0.06/kWh $1.11; or $0.09/kWh At $3.00/gal., 1 Kg of gas costs $1.11; or $0.09/kWh For equal energy (as H 2 ) Al can be cost competitive with gasoline; so its all about supply chain infra-structure *For the future, Al recycling could be done at solar photovoltaic farms and/or wind turbines sites. **The Al smelted by electrolysis has a CO 2 ratio of 1/3 compared with CO 2 from burning gasoline. However, this CO 2 could be sequestered Costs to reduce Al+3 to Al (cont.)

Oh, if only there were a real and reliable fuel cell technology that could deliver 100 KW for $50/kW For a fuel cell plus electric motor powered car: If we assume a 300 mi trip, a fuel cell times electric motor efficiency of 60%, only 1/3 of 47 Kg plus 1/3 x 60 Kg water = = 36 Kg of fuel weight compared with 16.2 Kg of gasoline for a Prius hybrid car. If we assume a 300 mi trip, a fuel cell times electric motor efficiency of 60%, only 1/3 of 47 Kg plus 1/3 x 60 Kg water = = 36 Kg of fuel weight compared with 16.2 Kg of gasoline for a Prius hybrid car. For the fuel cell powered car: ($0.26/Kg Al) x 16 Kg Al. = $4.10/300 mi. trip (wholesale) For the Prius: $18/300 mi trip (retail) Costs to reduce Al+3 to Al (cont.)

What about gallium and GaInSn? Ga,In and Sn are inert and totally recoverable. Experiments have recycled the Ga used in water splitting solid alloys up to 32 times. Currently, the 60 ton market for Ga is for electronics with purities between 4 and 7-9s, about $0.60/gm!!!!! Our process runs on low purity Ga,In,Sn and low purity Al and tap water/non potable water. Our analysis shows that with multiple reuse, a price of the alloy component charge of $0.70/kg can be realized. For fuels with <5% Ga there is enough economically recoverable Ga to run 10 9 cars.

1st order economics of our process Cost components per Kg of $2.42/Kg (retail) a. Bauxite mining and alumina separation - $0.44 b. Alumina purification and particle sizing - $1.32 c. Electrolysis of alumina to Al - $0.66 Energy content of 1 Kg of Al: 8.8 kW-Hrs Energy content of 1 Kg of gasoline: 12.8 kW-Hrs Cost of 50 Kg Al: 1st retail price, $2.42, plus 49 $0.66/Kg = $34.74; Average cost per Kg = $0.69 Cost of 2.5 Kg Ga,In,Sn; 1st 0.05 retail price, $250/Kg, plus 49 $0.10/Kg =$12.74; or $5.10/Kg Average cost per 0.05 Kg of Ga,In,Sn = $0.25 Cost of Al Alloy = ($0.94/8.8 kWh) = $0.11/ kWh (H2 + heat) Cost of Al Alloy = ($0.94/8.8 kWh) = $0.11/ kWh (H2 + heat) Cost of $3.00/gal = $0.09/kWh Cost of $3.00/gal = $0.09/kWh

Disclaimer: Visions won’t come true by themselves. An industry will embrace change out of either inspiration or desperation. I hope this talk leads toward inspiration. 40

Ga - In - Sn Ternary Phase Diagram 41

Enabling Wind or Solar as Base Load Electric Power Model Flow Diagram reaction tank, 95-5 alloy, and controls H20H20 H 2, 4.4 kWh/Kg-alloy 24/7 or on demand Fuel Cell or Gas Turbine/Generator H20H20 Electricity Heat, 4.4 kWh/Kg-alloy 24/7 or on demand Steam Turbine alumina, Ga,In,Sn + H 2 0 component separation H20H20 Ga,In,Sn recovery alumina electrolysis 12.9 kW-Hrs/Kg Al 95-5 alloy regeneration intermittent electrical power, e.g. solar or wind 42

Energy Source (wind, solar, nuclear, geothermal, etc) (-12.9 kWh/kg-Al) Energy Source (wind, solar, nuclear, geothermal, etc) (-12.9 kWh/kg-Al) Application (fuel cell, combustion engine) Application (fuel cell, combustion engine) Water Aluminum Alloy Aluminum Oxide Heat (+4.4 kWh/kg-Al) Heat (+4.4 kWh/kg-Al) Energy Water Reaction Hydrogen (+4.4 kWh/kg-Al) Hydrogen (+4.4 kWh/kg-Al) The Aluminum-Hydrogen Cycle CO 2 Sequestered 43

Coal from Wyoming

Primary metal: made from ore Native metal: 45

Challenges/issues Heat use/management – a big deal!! Infrastructure/supply chain to manufacture alloys and recycle them Current energy efficiency is only 34%, i.e. energy from H 2 /recycle energy x100 = 34% (industrial water electrolysis about 30%) If not recycled, the weight of needed water equals 2x the weight of alloy used. 46

Jerry M. Woodall National Medal of Technology Laureate, Barry and Patricia Epstein Distinguished Professor School of Electrical and Computer Engineering, Discovery Park, Purdue University, West Lafayette, IN 47906, USA Bulk Aluminum Alloys: A High Energy Density Material for Safe Energy Storage, Transport, and Splitting Water To Make Hydrogen on Demand

Primary metal to energy cycle 48 Bauxite Primary Aluminum Aluminum Alloy Hydrated Alumina Energy Out Energy In